CN100415902C - Method of improving steel object surface hardness using carbon distribution - Google Patents
Method of improving steel object surface hardness using carbon distribution Download PDFInfo
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- CN100415902C CN100415902C CNB2006100296909A CN200610029690A CN100415902C CN 100415902 C CN100415902 C CN 100415902C CN B2006100296909 A CNB2006100296909 A CN B2006100296909A CN 200610029690 A CN200610029690 A CN 200610029690A CN 100415902 C CN100415902 C CN 100415902C
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Abstract
The present invention relates to a method for raising steel component surface hardness by adopting carbon distribution, belonging to the field of heat treatment technology. Said method includes the following steps: firstly, coating side surface of workpiece with a layer of coating layer which is resistant to high temperature and does not transfer heat, then austenizing said workpiece and promptly placing the austenized workpiece into quenching medium, the interior of workpiece side surface which is not coated with heat-resisting coating layer can be instantaneously converted into martensite and most of side surface coated with heat-resisting coating layer still is austenite, then promptly quenching workpiece up to 200-400 deg.C, and heat-insulating for 10-2000s, in this course the carbon can be quickly diffused into side surface austenite from martensite so as to make its surface richly contain carbon, finally making the workpiece be quenched in water, so that the workpiece side surface can be hardened.
Description
Technical field
What the present invention relates to is the method in a kind of heat treatment technics field, specifically is that a kind of carbon that adopts distributes the method that improves steel object surface hardness.
Technical background
The thermo-chemical treatment of steel is surface alloying and a kind of technology of heat treatment phase bonded, and it reaches the purpose that improves its use properties by changing the composition and the tissue of steel-iron components upper layer.Carburizing be wherein a kind of the most frequently used also be crucial surface chemical heat-treatment process.Surface such as gear, bearing need have certain rigidity, wear resistance, contact and chafing fatigue performance, and the microstructure of the cementation zone that carburizing produced is cryptocrystal or the granular carbide of thin brilliant martensite and some amount and an amount of residual austenite, thereby layer surface has high hardness and antiwear property.The technological process more complicated of carburizing treatment needs the various processing parameters of choose reasonable, for example carburizing temperature.High temperature can be quickened the diffusion of carbon, and improves the solubleness of carbon in austenite, thereby shortens carburizing time, but too high temperature can make the cementation zone crystal grain of steel part thick, reduces and increase part deformation equipment life.General carburizing treatment all needs several hrs to tens hour, and production efficiency is not high.In addition, after carburizing finished, workpiece generally also needed thermal treatment, as quenching and tempering.
Find through literature search prior art, the principle that carbon distributes set forth in " the Carbon partitioning into austenite after martensitetransformation " that J.Speer etc. deliver on Acta Materialia 51 (material journal) (2003) P2611-2622 (austenite to carbon after the martensitic transformation in the distribution between a martensite and the austenite) literary composition between martensite and residual austenite, distribution by carbon can realize the rich carbon of austenite, but does not have the concrete content of mentioning technology.
Summary of the invention
The present invention provides a kind of carbon that adopts to distribute the method that improves steel object surface hardness on the basis of existing technology, need not complex apparatus for chemical carburizing, and it is simple to have technological process, and the cycle is short, characteristic of low energy consumption.
The present invention is achieved by the following technical solutions, may further comprise the steps:
1) with workpiece (gear, bearing housing etc.) the high temperature resistant and athermanous coating of the coated one deck of part surface (side), for example aluminum oxide or zirconia ceramics coating, heating makes it whole austenitizings then;
2) workpiece is quenched in the liquid quenching mediums such as Sn-Bi, Pb-Sn or Pb-Bi, do not had the zone of coating protection that martensitic transformation will take place;
3) with the workpiece up-quenching to 200-400 ℃ medium, and under this temperature, be incubated 10-1000s, carbon diffuses to the surperficial austenite region of coated protection by inner martensite, makes the rich carbon of top layer austenite;
4) workpiece is quenched to water, then obtained the hardened layer of surface martensite and residual austenite, the about 0.5-1mm of its thickness.
Among the present invention, add and suppress the element that carbide is separated out, as silicon, aluminium, (addition silicon is 0.5%-10.0% to alloying elements such as phosphorus, and aluminium is 0.2%-5.0%, massfraction), allow a large amount of carbon can be by in the austenite that quickly diffuses to the top layer in the martensite in isothermal processes.
Among the present invention, according to the composition selective quenching medium temperature of workpiece, according to M
sAnd M
fTemperature and formula Vm=1-exp[a (Ms-T)] quenching temperature in the time of can obtaining obtaining martensite.In the formula, Vm is the martensitic transformation amount, and Ms is that martensite begins transition temperature, can find from handbook, and a is the coefficient relevant with material, can measure by thermal dilatometer for different steel grades.The temperature T of liquid quenching medium is corresponding to the temperature of Vm=80%～90%.
The present invention after quenching immediately up-quenching to 200-400 ℃ medium; and under this temperature, be incubated 10-1000s; carbon is diffused to the austenite surf zone of coated protection by martensite; make the rich carbon of top layer austenite; quenching subsequently obtains the martensite and the remaining rich carbon austenitic of high carbon content to the water, in the hope of obtaining high rigidity and wear resistance.
The present invention is according to the carbon content of workpiece itself and the surface that obtains to have different carbon contents and enriched carbon layer thickness by the thickness that changes the side coating.The selection of coat-thickness keeps austenitic state to be as the criterion with the zone that can make workpiece be coated when workpiece quenches, and promptly selects the thickness of coating according to the character of composition, size and the quenchant of workpiece and coating, generally gets 0.5-2.5mm.The size of workpiece is more little, and hardening capacity is big more, and the cooling of quenchant is strong more, and coating obtains thick more.
The present invention is applicable to siliceous, and the low alloy steel of elements such as aluminium because these elements can be restrained separating out of cementite, helps carbon and distributed in austenite by martensite.Can not contain a large amount of strong carbide forming elements in the steel, but the strong carbide forming element of (massfraction＜0.2%) of minute quantity still is passable.Simultaneously the hardening capacity of workpiece to get well or size less, otherwise can not obtain the martensite of q.s after quenching.
The present invention has proposed the inner carbon of low alloy steel and has distributed the method that makes part surface (side) carburetting according to the principle that carbon distributes, and has avoided traditional carburization process complexity, the shortcoming that the cycle is long.Be specially adapted to the surface treatment of low alloy steel.
Embodiment
Provide following examples in conjunction with content of the present invention:
Embodiment 1: with containing 0.5% aluminium, the medium carbon alloy steel of 1.5% silicon replaces traditional 45# steel and makes gear (gear diameter 6mm), surveys outside gear earlier and coats aluminum oxide coating layer.The selection of coat-thickness keeps austenitic state to be as the criterion with the zone that can make workpiece be coated when workpiece quenches, and gets 1.5mm.Workpiece is heated to 820 ℃ of insulation 5min, quench then to 220 ℃-350 ℃ Sn-Bi quenching medium, the gear middle portion is finished after the martensitic transformation immediately up-quenching to 200 ℃-380 ℃ and be incubated 30s～1200s under this temperature, this moment, carbon was dispensed to by martensite in the austenite on top layer, and last shrend is to room temperature.
Embodiment 2: with containing aluminium 0.5%, the soft steel of silicon 1.8% replaces 20Cr steel commonly used and makes gear (gear diameter 20mm), outside gear, survey earlier and be coated with last layer zirconia ceramics coating, the selection of coat-thickness keeps austenitic state to be as the criterion with the zone that can make workpiece be coated when workpiece quenches, and gets 2.0mm.Workpiece is heated to 900 ℃ of insulation 5min, quench then to lead-Xi quenching medium of 220 ℃-350 ℃, the gear middle portion is finished after the martensitic transformation immediately up-quenching to 350 ℃-420 ℃ and be incubated 20s～1600s under this temperature, this moment, carbon was dispensed to by martensite in the austenite on top layer, and last shrend is to room temperature.
Embodiment 3: with containing 0.2% aluminium, the medium carbon steel of 1.6% silicon replaces the 45# steel and makes bearing housing, surveys face and outer side within it and is coated with the last layer aluminum oxide coating layer.The selection of coat-thickness keeps austenitic state to be as the criterion with the zone that can make workpiece be coated when workpiece quenches, and gets 1.5mm.After workpiece is heated to 820 ℃ of insulations, quench to lead-Xi quenching medium of 220 ℃-350 ℃, finish after the martensitic transformation up-quenching to 350 ℃-380 ℃ of ℃ of insulation 20s～1500s immediately, this moment, carbon was dispensed to by martensite in the austenite on top layer, and last shrend is to room temperature.
Embodiment 4: with containing 3.0% aluminium, 0.6% silicon soft steel replaces the 20Cr steel and makes the cylinder shape bearing housing, survey bearing housing outside earlier and be coated with last layer zirconia ceramics coating, the selection of coat-thickness is as the criterion with the zone maintenance austenitic state that can make workpiece be coated when workpiece quenches, and gets 2.5mm.Workpiece is heated to 900 ℃ of insulation 5min, quench then to 220 ℃-350 ℃ Sn-Bi quenching medium, finish after the martensitic transformation up-quenching to 350 ℃-420 ℃ of insulation 20s～1600s immediately, this moment carbon to the austenite on top layer, last shrend is to room temperature by the martensite partition.
Claims (5)
1. a method that adopts carbon distribute to improve steel object surface hardness is characterized in that, to containing 0.5-3.0% aluminium, in the 0.6-1.8% silicon, low-carbon alloy steel makes gear and bearing housing is handled, may further comprise the steps:
1) with the high temperature resistant and athermanous coating of the coated one deck of side surface of workpiece, heating makes it whole austenitizings then;
2) workpiece is quenched in the liquid quenching medium, do not had the zone of coating protection that martensitic transformation will take place;
3) with the workpiece up-quenching to 200-400 ℃ medium, and under this temperature, be incubated 10-1000s, carbon diffuses to the surperficial austenite region of coated protection by inner martensite, makes the rich carbon of top layer austenite;
4) workpiece is quenched to water, then obtained the hardened layer of surface martensite and residual austenite.
2. employing carbon according to claim 1 distributes the method that improves steel object surface hardness, it is characterized in that described high temperature resistant and athermanous coating is aluminum oxide or zirconia ceramics coating, and coat-thickness is 0.5-2.5mm.
3. employing carbon according to claim 1 distributes the method that improves steel object surface hardness, it is characterized in that described liquid quenching medium is Sn-Bi, Pb-Sn or Pb-Bi liquid.
4. distribute the method that improves steel object surface hardness according to claim 1 or 3 described employing carbon, it is characterized in that, described liquid quenching medium, its temperature is specially: according to M according to the one-tenth component selections of workpiece
sAnd M
fRelational expression Vm=1-exp[a (the M of temperature and martensitic transformation amount and temperature T
s-T)] quenching temperature when obtaining obtaining martensite, in the formula, Vm is the martensitic transformation amount, M
s, M
fBe respectively Ms (martensite start) point and termination temperature, T is at M
sAnd M
fBetween; A is the coefficient relevant with material, can measure by thermal dilatometer, and the temperature T of liquid quenching medium is corresponding to the temperature of Vm=80%～90%.
5. employing carbon according to claim 1 distributes the method that improves steel object surface hardness, it is characterized in that the hardened layer of described martensite and residual austenite, its thickness are 0.5-1mm.
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| CN100415902C true CN100415902C (en) | 2008-09-03 |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101705345B (en) * | 2009-09-02 | 2011-06-01 | 北京科技大学 | Process method for improving ductility and toughness of Cr-containing high-strength steel by utilizing carbon distribution |
| CN101818234B (en) * | 2010-04-20 | 2011-07-13 | 广州市型腔模具制造有限公司 | Quenching process of H13 steel for compression molds |
| CN102021479B (en) * | 2010-12-13 | 2012-08-01 | 首钢总公司 | Si-containing medium carbon steel and thermal treatment method for Si-containing medium carbon steel to obtain high strength and elasticity |
| CN102758207A (en) * | 2012-06-29 | 2012-10-31 | 上海市机械制造工艺研究所有限公司 | Complex heat treatment technology capable of improving surface performance of steel workpiece |
| CN103343191A (en) * | 2013-07-22 | 2013-10-09 | 哈尔滨工业大学 | Two-step isothermal heat treatment method for strengthening and toughening medium carbon-manganese-vanadium low alloy steel |
| DE102015016656A1 (en) * | 2015-12-19 | 2017-06-22 | GM Global Technology Operations LLC (n. d. Ges. d. Staates Delaware) | A method of making a coated hot worked cured body and a body made by the method |
| CN106011398B (en) * | 2016-05-31 | 2018-01-23 | 桂林电子科技大学 | The Technology for Heating Processing of low-alloy wear-resistant steel |
| CN106424280B (en) * | 2016-11-30 | 2017-09-29 | 华中科技大学 | A kind of high-strength steel hot forming differentiation mechanical property distribution flexible control method |
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2006
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Patent Citations (6)
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|---|---|---|---|---|
| JPS56150136A (en) * | 1980-04-24 | 1981-11-20 | Nippon Steel Corp | Cooling method for hot rolled wire rod |
| EP0090749A1 (en) * | 1982-03-25 | 1983-10-05 | Cegedur Societe De Transformation De L'aluminium Pechiney | Process for cooling metallurgical workpieces with minimized deformation |
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Assignee: Jiangsu Tianshun Metal Material Group Co., Ltd. Assignor: Shanghai Jiao Tong University Contract record no.: 2012320000445 Denomination of invention: Method of improving steel object surface hardness using carbon distribution Granted publication date: 20080903 License type: Common License Open date: 20070131 Record date: 20120412 |
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